SOLUTION: Two boys can mow a lawn in 2 hours and 30 minutes. If they are joined by three other boys, how many hours will it take to mow the lawn? A)1 hr B) 1 1/4 hrs C)1 1/2 hrs D)1 3/4

Question 1190088: Two boys can mow a lawn in 2 hours and 30 minutes. If they are joined by three other boys, how many hours will it take to mow the lawn?
A)1 hr B) 1 1/4 hrs C)1 1/2 hrs D)1 3/4 hrs E) 2 hrs

Found 4 solutions by math_tutor2020, ikleyn, josgarithmetic, Alan3354:
Answer by math_tutor2020(3817)   (Show Source): You can put this solution on YOUR website!

1 hr = 60 min
2 hr = 120 min
2 hr, 30 min = 120 min + 30 min = 150 min

Let's say the lawn has a total area of 300 sq ft
Each boy will handle 300/2 = 150 sq ft

Each individual has a unit rate of
rate = (amount done)/(time)
rate = (150 sq ft)/(150 min)
rate = 1 sq ft per min

Assume that the 3 other boys will have the same unit rate
If so, then the combined rate of all five boys is 5 sq ft per min. This assumes that no person hinders another.

rate = (amount done)/(time)
rate*time = amount done
time = (amount done)/(unit rate)
time = (300 ft^2)/(5 sq ft per min)
time = 60 min
time = 1 hour

Answer: A) 1 hour

Answer by ikleyn(52786)   (Show Source): You can put this solution on YOUR website!
.
Two boys can mow a lawn in 2 hours and 30 minutes. If they are joined by three other boys,
how many hours will it take to mow the lawn?
A)1 hr B) 1 1/4 hrs C)1 1/2 hrs D)1 3/4 hrs E) 2 hrs
~~~~~~~~~~~~~~

If two boys can mow a lawn in 2 hours and 30 minutes, it means that one boy, working alone, needs twice as much time, which is 2 hours 30 minutes + 2 hours 30 minutes = 5 hours. Hence, 5 boys working together, will complete the job in 5:5 = 1 hour. The ANSWER is option (C).

            Alternative way to solve the problem is to use boy-minutes as a measure of the entire job, by analogy with men-days.

The entire job is 2*150 = 300 boy-minutes. Hence, 5 boys will complete the job in 300:5 = 60 minutes = 1 hour. ANSWER

Solved.

Answer by josgarithmetic(39617)   (Show Source): You can put this solution on YOUR website!
Two plus three, would be 5 boys.
Five boys will work at a rate times the rate of just two boys.

For any 1-boy rate r,
1 for how many lawns for one-job,
x, how much time for the five boys,

Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
Assuming all boys are the same makes no sense.
RELATED QUESTIONS
Suppose one person can mow a lawn in x hours and a second person can mow the same lawn in (answered by richwmiller)
Gardener A can mow an entire lawn in 1 hour less than gardener B .If they work together... (answered by psbhowmick)
Ted can mow a lawn in 5 hours while eliot can mow the same lawn in 8 hours. How long will (answered by josmiceli)
I want to mow my lawn this summer but I need a new lawn mower. I can choose a riding... (answered by stanbon)
If bob can mow a lawn in 5 hours, and jim can mow the same lawn in 3 hours,how long will... (answered by mananth)
Sam can mow a lawn in 30 minutes. Melissa can mow the same lawn in 90 minutes. How long... (answered by Boreal,greenestamps,Alan3354)
siam can mow a lawn in 60 minutes. larry can mow the same lawn in 30 minutes . How long (answered by josmiceli,Alan3354)
Mo can mow a lawn in 4 hours. His twin brother Joe can mow the same lawn in 5 hours. How... (answered by nerdybill)
Gregory can mow the family's lawn in 3 hours, and Jennifer can mow it in 4 hours. If they (answered by ankor@dixie-net.com)